i am having problems with some coursework and i need to understand how ohm's law can back up my results that a longer wire is more resistant. please help im having a nightmare.
2007-01-17 06:08:45 · 7 answers · asked by olly_oconnell10 1 in Science & Mathematics ➔ Physics
Resistance of a wire is given in ohms/meter. To obtain the actual resistance you multiply this value by the length in meter.
So the more meters you have the more ohms!
2007-01-17 06:16:32 · answer #1 · answered by catarthur 6 · 0⤊ 0⤋
The simplest statement of Ohm's law: V=IR
If you measure voltage and current, you can calculate the resistance of your wire and presumably confirm that the longer one has more resistance.
To go a bit deeper to justify why the longer wire has more resistance, use Ohm's law (better version): Current density equals the dot product of conductivity times the electric field in the conductor.
So for a wire of fixed width, current density is proportional to current. Conductivity is fixed. So current is proportional to the E-field in the wire. The voltage is just the E-field times the length. So the voltage goes like the current times the length. Combined with the V=IR version of Ohm's law, this means that the resistance is proportional to the length of the whire.
2007-01-17 06:24:53 · answer #2 · answered by Anonymous · 0⤊ 0⤋
Ohm's law relates the current, voltage, and resistance to each other. So if you apply a fixed voltage to different lengths of wire and measure the current in each case, the decreasing current, plugged into the E=IR formula would show increased resistance.
2007-01-17 06:15:42 · answer #3 · answered by Mike1942f 7 · 0⤊ 0⤋
If one wire has more resistance than another, then the voltage drop across that wire will be greater. You will need a very sensitive meter to detect this. You could also show that the current flow through the longer wire is less when the voltage is kept constant (regulated).
2007-01-17 06:30:10 · answer #4 · answered by davidosterberg1 6 · 0⤊ 0⤋
The resistance of a wire is a function of its length and cross section area and resistivity.
As you can see from the definintion, lengthening a wire or decreasing its cross section increases the resistance.
Definitions
The electrical resistivity Ï (rho) of a material is usually defined by the following:
R = rho*L/A
where
Rho is the static resistivity (measured in ohm meters - Ωm)
R is the electrical resistance of a uniform specimen of the material (measured in ohms - Ω)
L is the length of the specimen (measured in meters - m)
A is the cross-sectional area of the specimen (measured in square meters - m²)
2007-01-17 06:18:09 · answer #5 · answered by modulo_function 7 · 0⤊ 0⤋
Apply the same DC voltage to two different lengths of wire (..make sure the wire guage is the same for both lengths..) Measure the current through each length. The longer piece of wire will have less current. R = E * I
2007-01-17 06:15:28 · answer #6 · answered by Chug-a-Lug 7 · 0⤊ 0⤋
r=v/i in ohms laws....
so find the resistance of the longer wire by using multimeter(to check calculations or else no need to)
then just use the same voltage u used for the experiment,
then the current,
then r=...just put in watever the figures u used in the experiement the voltage n current and u should get +/- the same as wat u mesured practically.
o.o i hope i answered it right or did i just read it wrong...
2007-01-17 06:21:11 · answer #7 · answered by Gandalf 6 · 0⤊ 0⤋